Exploiting the Phase in Diffusion MRI for Microstructure Recovery: Towards Axonal Tortuosity via Asymmetric Diffusion Processes

We derive the Ensemble Average Propagator (EAP) for the case of straight axons (White Matter tissue elongation) and for undulated axons having different tortuosity rates (WM tissue compression). We show that under the hypothesis of having both the Magnitude and Phase of the dMRI signal we can quantify the asymmetry of the EAP which is related to the rate of tortuosity variation in the compressed axon.